gcc: update to version 7.4.0, Add config options

for coping libc.a, libpthread.a and libstdc++ to target.
Add config option to eliminate need for -lstdc++ and -lgcc_pic
switches when linking statically

Signed-off-by: Noble Pepper <noblepepper@gmail.com>

devel/gcc/patches/300-mips_Os_cpu_rtx_cost_model.patch

@@ -1,9 +1,16 @@
-Use the proper rtx cost model for the selected CPU, even when optimizing
-for size. This generates better code.
+commit ecf7671b769fe96f7b5134be442089f8bdba55d2
+Author: Felix Fietkau <nbd@nbd.name>
+Date:   Thu Aug 4 20:29:45 2016 +0200
+
+gcc: add a patch to generate better code with Os on mips
+
+Also happens to reduce compressed code size a bit
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
 
 --- a/gcc/config/mips/mips.c
 +++ b/gcc/config/mips/mips.c
-@@ -17483,7 +17483,7 @@ mips_option_override (void)
+@@ -19790,7 +19790,7 @@ mips_option_override (void)
      flag_pcc_struct_return = 0;
  
    /* Decide which rtx_costs structure to use.  */